In-plane switching mode liquid crystal display device and manufacturing method thereof

ABSTRACT

In the typical IPS-LCD device with a wide viewing angle, since the metallic black matrix of the upper substrate affect the voltage between the common and pixel electrodes, the black matrix is made of resin and cannot be formed with a bent portion because of the limits of the processing technology. Therefore, the typical IPS-LCD device has a limit for effective realization and a low aperture ratio.  
     In the disclosed IPS-LCD device, since one of the common electrodes is formed to cover the data line and operate as the black matrix, the black matrix of the upper substrate can be made of resin and the driving voltage can be reduced. Therefore, actually, the multi-domain IPS-LCD device can be fabricated without the increase of driving voltage and decrease of aperture ratio.  
     Furthermore, since the common and pixel electrodes are formed on the same layer, the aperture ratio can be improved and the problems such as residual images or flicker can be solved.

[0001] This application claims the benefit of Korean Patent ApplicationsNo. 2000-0067516, filed on Nov. 14, 2000 and No. 2001-0002969, filed onJan. 18, 2001, which are hereby incorporated by reference as if fullyset forth herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a liquid crystal display device,and more particularly to a liquid crystal display device implementingin-plane switching. (IPS) where an electric field to be applied toliquid crystal is generated in a plane parallel to a substrate.

[0004] 2. Discussion of the Related Art

[0005] A typical liquid crystal display (LCD) device uses opticalanisotropy and polarization properties of liquid crystal molecules. Theliquid crystal molecules have a definite orientational order inalignment resulting from their thin and long shapes. The alignmentdirection of the liquid crystal molecules can be controlled by applyingan electric field to the liquid crystal molecules. In other words, asthe alignment direction of the electric field is changed, the alignmentof the liquid crystal molecules also changes. Since the incident lightis refracted to the orientation of the liquid crystal molecules due tothe optical anisotropy of the aligned liquid crystal molecules, imagesare displayed.

[0006] Generally, typical LCD devices include upper and lower substrateswith liquid crystal molecules interposed therebetween. The upper andlower substrates are generally referred to as color filter and arraysubstrates, respectively. The upper and lower substrates respectivelyinclude electrodes disposed on opposing surfaces of the upper and lowersubstrates. An electric field is generated by applying a voltage to theelectrodes, thereby driving the liquid crystal molecules to displayimages depending on light transmittance.

[0007] Of the different types of known LCDs, active matrix LCDs(AM-LCDs), which have thin film transistors and pixel electrodesarranged in a matrix form, are the subject of significant research anddevelopment because of their high resolution and superiority indisplaying moving images. Driving methods for such LCDs typicallyinclude a twisted nematic (TN) mode and a super twisted nematic (STN)mode.

[0008] However, the operation mode of the TN- or STN-LCD panel has adisadvantage of a narrow viewing angle. That is to say, the TN liquidcrystal molecules rotate with polar angles 0 to 90 degrees, which aretoo wide. Because of the large rotating angle, contrast ratio andbrightness of the TN- or STN-LCD panel fluctuate rapidly with respect tothe viewing angles.

[0009] To overcome the problem, an in-plane switching (IPS) LCD panelwas developed. The IPS-LCD devices typically include a lower substratewhere a pixel electrode and a common electrode are disposed, an uppersubstrate having no electrode, and a liquid crystal interposed betweenthe upper and lower substrates. Therefore, the IPS-LCD panel implementsa parallel electric field that is parallel to the substrates, which isdifferent from the TN- or STN-LCD panel and has advantages in contrastratio, gray inversion, and color shift that are related to the viewingangle.

[0010] A detailed explanation about operation modes of a typical IPS-LCDdevice will be provided with reference to FIGS. 1 to 5.

[0011] As shown in FIG. 1, upper and lower substrates 1 and 2 are spacedapart from each other, and a liquid crystal 3 is interposedtherebetween. The lower and upper substrates are called array and colorfilter substrates, respectively. Pixel and common electrodes 4 and 5 aredisposed on the lower substrate 2. The pixel and common electrodes 4 and5 are parallel with and spaced apart from each other. A color filter 7is disposed on a surface of the upper substrate 1 and opposes the lowersubstrate 2. The pixel and common electrodes 4 and 5 apply an electricfield 6 to the liquid crystal. The liquid crystal has a negativedielectric anisotropy, and thus it is aligned parallel with the electricfield 6.

[0012] FIGS. 2 to 5 conceptually illustrate operation modes of a typicalIPS-LCD device. When there is no electric field between the pixel andthe common electrodes 4 and 5, the long axes of the liquid crystalmolecules 3 maintain an angle, for example, the angle is 45 degrees,from a line perpendicular to the parallel pixel and common electrodes 4and 5 as shown in FIG. 3. On the contrary, when there is an electricfield between the pixel and common electrodes 4 and 5, there is anin-plane electric field 6 parallel to the surface of the lower substrate2 between the pixel and common electrodes 4 and 5 because the pixel andcommon electrodes are formed on the lower substrate 2 as shown in FIG.4. Accordingly, the liquid crystal molecules 3 are twisted so as toalign the long axes thereof in the direction of the electric field,thereby being aligned such that the long axes thereof are parallel withthe line perpendicular to the elongated direction of the pixel andcommon electrodes 4 and 5 as shown in FIG. 5. By the above-mentionedoperation modes and with additional parts such as polarizers andalignment layers, the IPS-LCD device displays images. The IPS-LCD devicehas a wide viewing angle and low color dispersion characteristic.Specifically, the viewing angle of the IPS-LCD device is about 70degrees in direction of up, down, right, and left. In addition, thefabricating processes of this IPS-LCD device are simpler than othervarious LCD devices.

[0013]FIG. 6 is a schematic plan view of an array substrate of thetypical IPS-LCD device.

[0014] As shown, a pixel area is defined by a row gate line 11 and acolumn data line 41. A TFT “T”, the switching device, is formed at thecrossing of gate and data lines. In the pixel area, a common line 15 iselongated along the direction of the gate line 11 and a plurality ofcommon electrodes 16 connected to the common line 15 are elongated alongthe direction of the data line 41. Moreover, in the pixel area, aplurality of pixel electrodes 43, which are spaced apart from the commonelectrodes 16 and arranged in an alternating pattern, is connected tothe TFT “T” and the pixel line 45. The pixel line 45 overlaps the gateline 11 to make a storage capacitor “S”.

[0015] Therefore, in the IPS-LCD devices, since lateral electric fieldis formed between the common electrodes 16 and the pixel electrodes 43of the same plane and the liquid crystal molecules are aligned parallelto the lateral electric field, the viewing angle can be improved.Furthermore, the IPS-LCD devices have low color dispersion qualities andthe fabricating processes thereof are simpler than those of othervarious LCD devices.

[0016] However, because the common and pixel electrodes 16 and 43 aredisposed on the same plane on the lower substrate, the transmittance andaperture ratio are low. In addition, a response time according to adriving voltage should be improved and a cell gap should be uniformbecause of the low alignment margin. A color shift problem according tothe viewing angle still remains. These problems are dependent on therotational direction of the liquid crystal molecules under the electricfield over the threshold voltage and are generated from the increase ordecrease of the retardation and of the liquid crystal layer according tothe viewing angle.

[0017]FIG. 7 is a schematic plan view of an array substrate of theIPS-LCD device for solving the color shift problem.

[0018] As shown, upper and lower domains “A” and “B.” are formed bybending the common and pixel electrodes 16 and 43 at an angle withrespect to the common line 15. The electric field between two electrodes16 and 43 rotates the liquid crystal molecules 81 and 82 of the domains“A” and “B” in opposite direction from each other. A liquid crystalmolecule of the upper domain “A” is rotated clockwise and a liquidcrystal molecule of the lower domain “B” is rotated counter-clockwise.Therefore, the liquid crystal molecules 81 and 82 of two domains “A” and“B” are aligned in different directions to compensate the color shifteffectively.

[0019] Here, since the data line 41 is also bent at an angle withrespect to the common line 15 and is patterned parallel to the commonand pixel electrodes 16 and 43, the space between the data line 41 andthe common electrode 16 can decrease, and the aperture ratio can beimproved. To make the most of these advantages, a black matrix of anupper substrate also should have a bent portion. However, in the IPS-LCDdevice, since the metallic black matrix affects the voltage between thecommon and pixel electrodes 16 and 43, the black matrix is made ofresin, which cannot be formed with a bent portion because of the limitof the processing technology. Therefore, the IPS-LCD device of FIG. 7has a limit for effective realization.

[0020]FIGS. 8A to 8D are sequential cross-sectional views taken along aline “VIII-VIII” of FIG. 7 showing the fabrication process for the arraysubstrate of the typical IPS-LCD device.

[0021]FIG. 8A shows the step of patterning gate electrode 12, common andstorage electrodes 16 and 11 of a first metal layer, which can be madeof metal, for example, aluminum (Al) or chromium (Cr), on the substrate10.

[0022]FIG. 8B shows the step of forming a gate insulator 21 andpatterning an active layer 23 and an ohmic contact layer 25 on the firstmetal layer. The gate insulator 21 can be made of silicon nitride (SiNx)and the ohmic contact layer 25 is doped by impurities.

[0023]FIG. 8C shows the step of patterning another storage electrode 45and source 47, drain 49, pixel 43, electrodes and data line 41, of asecond metal layer. The source and drain electrodes 47 and 49 arepatterned on the ohmic contact layer 25 and the pixel electrodes 43 arespaced apart from the common electrodes 16 on the gate insulator 21.

[0024]FIG. 8D shows the step of forming a passivation layer 51, whichprevents the active layer 23 from contamination of mists or impurities,on the entire surface of the substrate.

SUMMARY OF THE INVENTION

[0025] Accordingly, the present invention is directed to an in-planeswitching liquid crystal display device and manufacturing method thereofthat substantially obviates one or more of problems due to limitationsand disadvantages of the related art.

[0026] An object of the present invention is to provide an in-planeswitching liquid crystal display device that has a wide viewing angleand a high aperture ratio and a manufacturing method thereof.

[0027] Another object of the present invention is to provide an in-planeswitching liquid crystal display device that has an improved color shiftand a manufacturing method thereof.

[0028] Additional features and advantages of the invention will be setforth in the description that follows, and in part will be apparent fromthe description, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

[0029] To achieve these and other advantages and in accordance with thepurpose of the present invention, as embodied and broadly described, anarray substrate for an in-plane switching liquid crystal display deviceincludes a substrate, a gate line extending along a first direction onthe substrate, a data line extending along a second direction on thesubstrate and having at least one bent portion, a thin film transistorconnected to the gate and data lines, a plurality of common electrodesextending along the second direction and having at least one bentportion, wherein at least one of the common electrodes overlaps aportion of the data line, a common line elongating along the firstdirection and connected to the plurality of common electrodes, aplurality of pixel electrodes alternated with the common electrodes andhaving at least one bent portion and a pixel line extending along thefirst direction and connected to the plurality of pixel electrodes.

[0030] In another aspect of the present invention, a method offabricating an array substrate includes forming a common line extendingalong a first direction, a plurality of common electrodes extendingalong a second direction and having a substantially zigzag shape, a gateline extending along the first direction and a gate electrode on asubstrate, forming a gate insulator on the gate and common lines,forming a semiconductor layer on the gate insulator, forming a data lineextending along the second direction having a substantially zigzag shapeand overlapping with at least one of the common electrodes and sourceand drain electrodes connected to the data line on the semiconductorlayer, forming a passivation layer on the data line and the source anddrain electrodes and forming a plurality of pixel electrodes extendingalong the second direction, having a substantially zigzag shape andalternated with the common electrodes and a pixel line connected to thepixel electrodes.

[0031] It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory and are intended to provide further explanation of theinvention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings, which are included to provide afurther understanding of the invention and are incorporated in andconstitute a part of this application, illustrate embodiments of theinvention and together with the description serve to explain theprinciple of the invention. In the drawings:

[0033]FIG. 1 is a schematic cross-sectional view of a typical IPS-LCDdevice;

[0034]FIGS. 2 and 3 are perspective views illustrating off stateoperation of the typical IPS-LCD device;

[0035]FIGS. 4 and 5 are perspective views illustrating on stateoperation of the typical IPS-LCD device;

[0036]FIGS. 6 and 7 are schematic plan views of array substrates of thetypical IPS-LCD device;

[0037]FIGS. 8A to 8D are sequential cross-sectional views taken along aline “VIII-VIII” of FIG. 7;

[0038]FIGS. 9A and 9B are schematic plan views of an array substrate ofthe IPS-LCD device according to the first and second embodiments of thepresent invention, respectively;

[0039]FIGS. 10A to 10E are sequential cross-sectional views taken alonga line “X-X” of FIG. 9A;

[0040]FIG. 11 is a schematic cross-sectional view taken along a line“XI-XI” of FIG. 9B;

[0041]FIGS. 12A and 12B are schematic plan views of an array substrateof the IPS-LCD according to the third and forth embodiments of thepresent invention, respectively;

[0042]FIGS. 13A to 13E are sequential cross-sectional views taken alonga line “XIII-XIII” of FIG. 12A;

[0043]FIG. 14 is a schematic cross-sectional view taken along a line“XIV-XIV” of FIG. 12B;

[0044]FIGS. 15A and 15B are schematic plan views of an array substrateof the IPS-LCD device according to the fifth and sixth embodiments ofthe present invention, respectively;

[0045]FIGS. 16A to 16F are sequential cross-sectional views taken alonga line “XVI-XVI” of FIG. 15A; and

[0046]FIG. 17 is a schematic cross-sectional view taken along a line“XVII-XVII” of FIG. 15B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] Reference will now be made in detail to the preferred embodimentsof the present invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

[0048]FIGS. 9A and 9B are schematic plan views of an array substrate ofthe IPS-LCD device according to a first embodiment and a secondembodiment of the present invention, respectively.

[0049] As shown in FIG. 9A and FIG. 9B, a gate line 111 and gateelectrode 113 are patterned on an insulating substrate (not shown). Agate insulator (not shown), for example, silicon nitride film (SiNx) orsilicon oxide film (SiO₂), is formed thereon. An active layer 131 ofamorphous silicon is patterned on the gate insulator of the gateelectrode 113 and an ohmic contact layer of doped amorphous silicon isformed thereon. Then a data line 141, which defines a pixel region bycrossing the gate line 111, and source and drain electrodes 143 and 145are patterned thereon. The data line 141 has a substantially zigzagshape. The data line 141 and the source and drain electrodes 143 and 145can be made of a metal. A passivation layer (not shown) is formedthereon and has a contact hole 153 exposing the drain electrode 145.Here, the passivation layer can be made of silicon nitride film (SiNx)or silicon oxide film (SiO₂) like the gate insulator, or organicmaterial such as benzocyclobutene (BCB), acrylate or polyimide. First tothird pixel electrodes 165, 166 and 167 having a substantially zigzagshape and first to third common electrodes 162, 168 and 169 having asubstantially zigzag shape are patterned in the pixel region on thepassivation layer. In the context of FIGS. 9A and 9B, the pixelelectrodes 165, 166 and 167 and the common electrodes 162, 168 and 169extend vertically and are spaced apart from each other horizontally. Thepixel electrodes 165, 166 and 167 are alternated with the commonelectrodes 162, 168 and 169. The first common electrode 162 overlaps aportion of the data line 141 in FIG. 9A or covers the data line 141 inFIG. 9B, and extends to another first common electrode of a neighboringpixel. A metal pixel line 149 is connected to the pixel electrodes 165,166 and 167 through the contact hole 155 and overlaps with the commonline 161 to form a storage capacitor (storage electrode). The firstpixel electrode 165 is connected to the drain electrode 145 through acontact hole 153. Here, the first to third common electrodes 162, 168and 169 and the pixel electrodes 165, 166 and 167 are formed oftransparent conductive material such as indium-tin-oxide (ITO) orindium-zinc-oxide (IZO), so that the aperture ratio can be improved.

[0050]FIGS. 10A to 10E are sequential cross-sectional views taken alonga line “X-X” of FIG. 9A.

[0051] As shown in FIG. 10A, a gate line 111 and a gate electrode 113are patterned on a substrate 100 such as glass. As shown in the contextof FIG. 9A, the gate line 111 extends horizontally.

[0052] As shown in FIG. 10B, a gate insulator 121 is formed on theentire surface of the substrate 100, and then an active layer 131 ofamorphous silicon or the like and an ohmic contact layer 133 of dopedamorphous silicon, for example, are patterned. Here, the gate insulator121 can be made of silicon nitride film (SiNx), silicon oxide film(SiO₂) or organic material such as BCB, acrylate, polyimide.

[0053] As shown in FIG. 10C, a data line 141, source and drainelectrodes 143 and 145 and a metal pixel line 149 of conductivematerial, such as metal or transparent conductive material, arepatterned. A pixel region is defined by the data line 141 crossing withthe gate line 111. Source and drain electrodes 143 and 145 are adjacentto each other with the gate electrode 113 below them and below the spaceseparating the source and drain electrodes 143 and 145. Here, the dataline 141 has a substantially zigzag shape and the metal pixel line 149operates as an upper electrode of a storage capacitor formed between theprevious gate line 111 and the metal pixel line 149.

[0054] As shown in FIG. 10D, a passivation layer 151 of silicon nitridefilm (SiNx), silicon oxide film (SiO₂) or organic material such as BCB,acrylate, or polyimide is formed on the entire surface of the substrate.Then contact holes 153 and 155, which expose the drain electrode 145 andthe metal pixel line 149, respectively, are patterned.

[0055] As shown in FIG. 10E, first to third pixel electrodes 165, 166and 167 and first to third common electrodes 162, 168 and 169 oftransparent conductive material such as ITO or IZO are patterned. Thefirst common electrode 162 overlaps a portion of the data line 141. Inthe context of the FIGS. 9A and 10A-E, the first to third pixelelectrodes 165, 166 and 167 and the first to third common electrodes162, 168 and 169 having a substantially zigzag shape are verticallyelongated and horizontally spaced apart from each other alternately.Even though the storage capacitor is mainly formed between the metalpixel line 149 and the previous gate line 111, it can be formed byanother structure as understood by one of skill in the art.

[0056]FIG. 11 is a schematic cross-sectional view taken along a line“XI-XI” of FIG. 9B, in which the first common electrode 162 covers thedata line 141.

[0057] Here, since the common electrode 162 overlaps or covers the dataline 141, the space between the data line 141 and the end of the commonelectrode 162 is narrow and the aperture ratio can be improved. To makethe most of these advantages, a black matrix of an upper substrate alsoshould have a bent or substantially zigzag portion. However, since theblack matrix made of resin cannot be formed with a bent portion becauseof the limits of the processing technology, the IPS-LCD device of FIGS.9A and 9B uses a metallic black matrix with a high driving voltage.

[0058] To improve this problem, other embodiments are suggested.

[0059]FIGS. 12A and 12B are schematic plan views of an array substrateof the IPS-LCD device according to a third embodiment and a fourthembodiment of the present invention, respectively.

[0060] As shown, a gate line 111 and gate electrode 113 are patterned onan insulating substrate (not shown). A common line 115 in substantiallythe same direction as the gate line 111 is patterned between arespective gate line 111 and first to third common electrodes 117, 118and 119. The first to third common electrodes have a substantiallyzigzag shape and extend from the common line 115 roughly perpendicularto the gate line 111. A gate insulator, for example, silicon nitridefilm (SiNx) or silicon oxide film (SiO₂), is formed thereon. An activelayer 131 of amorphous silicon is patterned on the gate insulator of thegate electrode 113 and an ohmic contact layer of doped amorphous siliconis formed thereon. Then a data line 141, which defines a pixel region bycrossing the gate line 111, and source and drain electrodes 143 and 145are patterned thereon. Here, the data line 141 has a substantiallyzigzag shape and overlaps the first common electrode 117 in FIG. 12A orcovers the first common electrode 117 in FIG. 12B. The data line 141 andthe source and drain electrodes 143 and 145 can be made of a metal. Apassivation layer (not shown) is formed thereon and has a contact hole153 exposing the drain electrode 145. Here, the passivation layer can bemade of silicon nitride film (SiNx) or silicon oxide film (SiO₂) likethe gate insulator, or organic material such as BCB, acrylate, orpolyimide. First to third pixel electrodes 165, 166 and 167 having asubstantially zigzag shape are patterned in the pixel region on thepassivation layer. In the context of FIGS. 12A and 12B, the first tothird pixel electrodes 165, 166 and 167 and the first to third commonelectrodes 117, 118 and 119 extend roughly vertically and are spacedapart horizontally. A pixel line 161 is connected to the pixelelectrodes 165, 166 and 167 and overlaps with the common line 115 toform a storage capacitor. The first pixel electrode 165 is connected tothe drain electrode 145 through a contact hole 153. Here, the common andpixel electrodes 117, 118, 119, 165, 166 and 167 and the data line 141can be patterned to have at least one bent portion.

[0061]FIGS. 13A to 13E and FIG. 14 are sequential cross-sectional viewstaken along a line “XIII-XIII” of FIG. 12A showing the fabricationprocess of the IPS-LCD of the third and fourth embodiments.

[0062] As shown in FIG. 13A, a gate line 111, a gate electrode 113, acommon line 115 and first to third common electrodes 117, 118 and 119are patterned on a substrate 100 such as glass. The first commonelectrode 117 has two branches. In the context of FIGS. 12A and 12B, thegate line 111 and the common line 115 extend horizontally. In thecontext of FIGS. 12A and 12B the common electrodes 117, 118 and 119having a substantially zigzag extend vertically and are connected to thecommon line 115. In this embodiment, even though the number of commonelectrodes is three for simplicity of description, the number can bechanged depending on the distance between the common electrodes or theslant angle of the common electrodes. The gate line 111, the common line115 and the common electrodes 117, 118 and 119 can be made ofnon-transparent material such as metal, for example, chromium (Cr),aluminum (Al), aluminum alloy, molybdenum (Mo), tantalum (Ta), tungsten(W), antimony (Sb), an alloy or a double layer thereof.

[0063] As shown in FIG. 13B, a gate insulator 121 is formed on theentire surface of the substrate 100 and then an active layer 131 ofamorphous silicon and an ohmic contact layer 133 of doped amorphoussilicon are patterned. Here, the gate insulator 121 can be made ofsilicon nitride film (SiNx), silicon oxide film (SiO₂) or organicmaterial such as BCB, acrylate, or polyimide.

[0064] As shown in FIG. 13C, a data line 141, source and drainelectrodes 143 and 145 of conductive material such as metal arepatterned. A pixel region is defined by the data line 141 crossing withthe gate line 111. Source and drain electrodes 143 and 145 are adjacentto each other and separated by a space, with the gate electrode 113below the source and drain electrodes 143 and 145 and the space. Here,the data line 141 has a substantially zigzag shape and overlaps with thefirst common electrode 117.

[0065] As shown in FIG. 13D, a passivation layer 151 of silicon nitridefilm (SiNx), silicon oxide film (SiO₂) or organic material such as BCB,acrylate, or polyimide is formed on the entire surface of the substrateand then a contact hole 153 exposing the drain electrode 145 ispatterned.

[0066] As shown in FIG. 13E, first to third pixel electrodes 165, 166and 167 and a pixel line 161 of transparent conductive material such asindium-tin-oxide (ITO) or indium-zinc-oxide (IZO) are patterned. In thecontext of FIGS. 12A and 12B, the first to third pixel electrodes 165,166 and 167 having a substantially zigzag shape extend vertically andare spaced apart from the corresponding common electrodes 117, 118 and119 horizontally. The pixel line 161 and pixel electrodes 165, 166 and167 can be made of non-transparent conductive material.

[0067] In the array substrate of the IPS-LCD device according to thethird embodiment of the present invention, since the data line 141overlaps the first common electrode 117 and the data line 141 and thefirst common electrode 117 operate as a black matrix, the black matrixof the upper substrate can have only the row line. Therefore, the blackmatrix of the upper substrate can be made of resin and the apertureratio can be improved by using the area near the data line 141 as apixel region. Moreover, in other embodiments, the common electrodes 117,118 and 119 can be patterned on the gate insulator 121.

[0068]FIG. 14 is a schematic cross-sectional view of an array substrateof the IPS-LCD device taken along a line “XIV-XIV” of FIG. 12B, in whichthe data line 141 covers the first common electrode 117.

[0069]FIGS. 15A and 151B are schematic plan views of an array substrateof the IPS-LCD device according to a fifth embodiment and a sixthembodiment of the present invention with the more improved apertureratio.

[0070] As shown, a gate line 111 and gate electrode 113 are patterned onan insulating substrate (not shown). A gate insulator (not shown), forexample, silicon nitride film (SiNx) or silicon oxide film (SiO₂), isformed thereon. An active layer 131 of amorphous silicon is patterned onthe gate insulator of the gate electrode 113 and an ohmic contact layerof doped amorphous silicon is formed thereon. Then a data line 141,which defines a pixel region by crossing the gate line 111, and sourceand drain electrodes 143 and 145 are patterned thereon. The data line141 has a substantially zigzag shape. The data line 141 and the sourceand drain electrodes 143 and 145 can be made of a metal. A passivationlayer is formed thereon and has a contact hole 153 exposing the drainelectrode 145. Here, the passivation layer can be made of siliconnitride film (SiNx) or silicon oxide film (SiO₂) like the gateinsulator, or organic material such as BCB, acrylate, or polyimide.First to third pixel electrodes 165, 166 and 167 and first to thirdcommon electrodes 171, 168 and 169 having a substantially zigzag shapeare patterned in the pixel region on the passivation layer. In thecontext of FIGS. 15A and 15B, the pixel electrodes 165, 166 and 167 andthe common electrodes 171, 168 and 169 extend roughly vertically and arespaced apart from each other horizontally. The pixel electrodes 165, 166and 167 are alternated with the common electrodes 171, 168 and 169. Thefirst common electrode 171 overlaps the data line 141 in FIG. 15A orcovers the data line 141 in FIG. 15B and extends to another commonelectrode of a neighboring pixel. A pixel line 161 is connected to thepixel electrodes 165, 166 and 167 and overlaps with the metal commonline 147, which is connected to the common line 164 through the contacthole 155, to form a storage capacitor. The storage capacitor can be madebetween the pixel line 161 and the previous or adjacent gate line. Thefirst pixel electrode 165 is connected to the drain electrode 145through a contact hole 153. Here, the first common electrode 171 isformed of non-transparent material such as metal and the other commonelectrodes 168 and 169, and the pixel electrodes 165, 166 and 167 andthe pixel line 161 are formed of transparent conductive material such asITO or IZO.

[0071]FIGS. 16A to 16F are sequential cross-sectional views taken alonga line “XVI-XVI” of FIG. 15A showing the fabrication process.

[0072] As shown in FIG. 16A, a gate line 111 and a gate electrode 113are patterned on a substrate 100 such as glass. The gate line 111 ishorizontally elongated.

[0073] As shown in FIG. 16B, a gate insulator 121 is formed on theentire surface of the substrate 100 and then an active layer 131, ofamorphous silicon and an ohmic contact layer 133 of doped amorphoussilicon are patterned. Here, the gate insulator 121 can be made ofsilicon nitride film (SiNx), silicon oxide film (SiO₂) or organicmaterial such as BCB, acrylate, or polyimide.

[0074] As shown in FIG. 16C, a data line 141, source and drainelectrodes 143 and 145 and a metal common line 147 of conductivematerial such as metal are patterned. The data line 141 defines a pixelregion by crossing with the gate line 111 and source and drainelectrodes 143 and 145 are adjacent to each other with the gateelectrode 113 below the source and drain electrodes 143 and 145 andbelow a space separating the source and drain electrodes 143 and 145.Here, the data line 141 has a substantially zigzag shape and the metalcommon line 147 operates as a lower electrode of a storage capacitor.

[0075] As shown in FIG. 16D, a passivation layer 151 of silicon nitridefilm (SiNx), silicon oxide film (SiO₂) or organic material such as BCB,acrylate, or polyimide is formed on the entire surface of the substrate,and then a contact hole 153 exposing the drain electrode 145 ispatterned. In the case of using organic material of low dielectricconstant such as BCB, acrylate or polyimide for the passivation layer,the interference of the first common electrode 171 voltage, whichresults from the overlap of the data line 141 and the first commonelectrode 171, can be minimized.

[0076] As shown in FIG. 16E, first to third pixel electrodes 165, 166and 167, a pixel line 161 and second and third common electrodes 168 and169 of transparent conductive material such as indium-tin-oxide (ITO) orindium-zinc-oxide (IZO) are patterned.

[0077] As shown in FIG. 16F, subsequently, the first common electrode171 of conductive material such as metal is patterned, connected to thecommon line 164 as in FIGS. 15A and 15B and overlaps a portion of thedata line 141. The first common electrode 171 can be made during thestep of forming the gate electrode 113. The other common electrodes 168and 169 and the pixel electrodes 165, 166 and 167 can be made oftransparent conductive material such as ITO or IZO, so that the dataline 141 also can be formed in the substantially zigzag shape regardlessof the material of the black matrix formed on the upper substrate, andthe transmittance and the aperture ratio can be improved. Here, in thecontext of FIGS. 15A and 15B, the first to third pixel electrodes 165,166 and 167 and the first to third common electrodes 171, 168 and 169having a substantially zigzag shape extend in roughly a verticaldirection and are spaced apart horizontally from each other in analternating pattern. Even though first to third pixel electrodes 165,166 and 167, a pixel line 161 and second and third common electrodes 168and 169 are patterned and then the first common electrode 171 ispatterned, the first common electrode 171 can be patterned before thethird pixel electrodes 165, 166 and 167, the pixel line 161 and thesecond and third common electrodes 168 and 169, which can be patternedlater. Even though the storage capacitor is formed between the metalcommon line 147 and the pixel line 161, another structure of storagecapacitor can be adopted as one of skill in the art would understand.

[0078]FIG. 17 is a schematic cross-sectional view of an array substrateof the IPS-LCD device taken along a line “XVII-XVII” of FIG. 15B, inwhich the first common electrode 171 covers the data line 141.

[0079] In the array substrate of the IPS-LCD device according to thefifth and sixth embodiments of the present invention, even though thefirst common electrode 171 that overlaps or covers the data line 141 ismade of opaque material such as Cr or Al, the second and third commonelectrodes 168 and 169 are made of transparent material such as ITO orIZO. Therefore, the aperture ratio can be improved by increase oftransmittance. Moreover, since the common and pixel electrodes areformed on the same layer, the problem of residual images can be solved.

[0080] Consequently, in the IPS-LCD device for wide viewing angle, sincethe common electrodes are made of a transparent material such as ITO orIZO and at least one common electrode overlaps or covers the data line,the aperture ratio can be improved and the problems such as residualimages or flicker can be solved with the metallic black matrix of theupper substrate. On the other hand, to decrease the power consumption, ablack matrix of the upper substrate should be made of resin. In otherembodiments, one of the common electrodes can be formed to overlappartially or to cover the data line and operate as the black matrix, sothat the black matrix of the upper substrate can be made of resin, andthe driving voltage and the power consumption can be reduced. Therefore,since the data line can be made in a substantially zigzag shaperegardless of the material of the black matrix formed on the uppersubstrate, the multi-domain IPS-LCD device actually can be fabricatedwithout increasing the driving voltage or decreasing aperture ratio.

[0081] It will be apparent to those skilled in the art that variousmodifications and variation can be made in the method of manufacturing aflat pane display device of the present invention without departing fromthe spirit or scope of the invention. Thus, it is intended that thepresent invention cover the modifications and variations of thisinvention provided they come within the scope of the appended claims andtheir equivalents.

1. An array substrate for an in-plane switching liquid crystal displaydevice, comprising: a substrate; a gate line and a data line on thesubstrate, the data line having at least one bent portion; a thin filmtransistor at a crossing portion of the gate and data lines; a pluralityof common electrodes having at least one bent portion, at least oneoverlapping common electrode overlapping at least a portion of the dataline; a common line connected to the common electrodes; and a pluralityof pixel electrodes alternated with the common electrodes, each pixelelectrode having at least one bent portion. 2-28. (Cancelled)